In biventricular pacing (BiVP), one wire or catheter is implanted in the right ventricle (RV) and another is threaded into a vein, the coronary sinus, which drains into the right atrium (RA) to pace the left ventricle (LV). The coronary sinus catheter is then guided to the lateral or posterior part of the left ventricle. Alternatively, a left ventricular lead can be implanted by thoracotomy (i.e., through a small incision between the ribs, the lead is implanted on the surface of the left ventricle) or even by crossing the atrial septum and inserting the lead inside the left ventricle. Yet, the exact and best position for each catheter position is difficult to determine at the time of insertion. In fact, there are no physiological means to determine the best site at the time of lead placement except possibly the use of echocardiography, which is time consuming and poses a problem in keeping the operative field sterile. Biventricular pacing (BiVP) reverses intraventricular conduction delay (IVCD) and left ventricular (LV) dysfunction (LVD) in CHF from dilated cardiomyopathy (DCM). BiVP is appealing because intraventricular conduction delay (IVCD) and left bundle branch block (LBBB) are intrinsic to advancing dilated cardiomyopathy (DCM) with LV dysfunction (LVD). 2-DE of the RV and LV free walls and interventricular septum (IVS) in DCM suggests that LBBB adversely affects the coordination of LV contraction (LV SYNC) and that BiVP, or “cardiac resynchronization therapy” (CRT), can improve LV SYNC. Many, but not all, patients derive clinical benefit from BiVP, and selection criteria are not fully developed. Insertion of permanent endocardial LV pacing leads via the coronary sinus (CS) is technically demanding, with a 10% failure rate. BiVP has not been carefully evaluated clinically as therapy for acute heart failure (ACHF).